Radio-phonograph combination



Aug. 15, 1950 J, MOIR' 2,519,063 7 RADIO-PHONOGRAPH COMBINATION Filed Oct. 25, 1947 Inventor: James Meir,

M 5 hM His Attorney.

Patented Aug. 15, 1950 aAmomuono GnAPmooMBINATIoN James-;Moin, RugbmEngland; tozGeneral- I Electric-Company;acornoratiomofiNewYork. Application October-25, 1947',"Serial No; 782126 InrGleat-Britaih November l', I946 'Ih'issinventiomr latesi melectroniccironits for:

reoeiving sig nali modulatedi carrier WEWBS}: and? its has: time its; primam', obj eat; to; provide: a; new and improved electronic, Gilfillity in-ywhichi as; stage:

thereon normally emploi ed fon-transl-atimrof' 5*;

high-frequency warefmay;be seleetively-employed for. amnlificationon audio; frequency;oscillations;

In moshcasea-wheredt. is desiredrto adapt a; radio receiver ion reproducing; soundnfrom a.

sloiaimet (c1. ire-4:00.11)

high frequency oscillations; The anode end"; of:

the-resistor is connected to; a. pointin; the circuit: arrangement 'subseguent to the demodulatingg stagethrough. a canacitorr cap-ahle'ofr passing-r audio frequency; oscillations; whereby; the circuit: arrangement is: rendered; oanabl'e; at will, eithen:

of. receiving signal modulated-carrier waves; or.-

amplifying, audio; irequencywoseillations applied to the. grid, of. saidieleotronidisohargeedevice with? phonographs record, or ten otherwise; amplifying: 111;; outmodifieatiom audio frequency signals, theaudioefrequency sig nale are: introduced; intha input, of the demo dulationstage of; the receiver. or intolth input ciruitpf. an, audio frequency. amplifying; tube.

For. a better. understanding. on the. invention:- reference be. hadrto the, followings descriptionetaken inlconnectiomwith theaccempanying' drawing and. its scope, will; he, pointed out in'- the Im the event. that the receiver is, constructed 175; n endedxclaims Thesinglafi llrecf theadraw only to, receive; signal,- modulateds carrier Wavesofi large amplitude, fort example in: a: receiver: adaptedinr, demndnlating; signaltmogiulated car.-- rienwauesimnressed; on-th innutloil the receiver-v ing represents a portion oflthacircuihof a.-radio. receiver. embodying myjnvention The neceiver.v illustrated in. the, drawing, may; conveniently consist; of L a single. frequ ncyfrom. a wired; circuit. or. is provided withs come 21 stage ll, a demodul'atingstage. L anda-single, low

naratively-t small; gain. on; the; audio, frequency: side; here. man be, insufficient. audio frequency. amplification in the receiver satisfaettmily toam Dliiy the audio, freolnenonoscillations arising: in

frequency stage. Such an anraneementrislene tirely adequate when theincomingsignahmodnv la'teioarrier wave is ..conyeyedlby{a-wired.circuit to; the innut tel'minali of; the .rec.eiv.er.. In such...

the ontputoi-Iaephonographcpichup. Inlthe r.e.--- 255ml.).arrangementath carrier wave, level would,

ceiizenhoweven,themmay be. present; prior to, the demodulating'. stage, of the, receiver, a, high freguencn amnlifying stageinsertedinn the punp se; ofi-enabling the receiver. to. have. a desired.

normally, be sufiici'ent to he demodulated directly:v andtlie demodulation; products appliedto. the. audio freguencystage 3"9;f the receiver., Such. anarrangement; howfeverj would' berelatively un seleotitityh (In..thi$. case the. gossibility arisen 0 selective and-the. introduction of, the high the another object.eithemesentinyentionto :prov-ide 4 an arrangement which ayoidsQ-the. use won internal, switching otherthanthati. essential, for, thecon ne t n intoithereceiyer eithesourceoi audio. frequency oscillations.

In a circuit arrangement. for, receiving signal modulated carrier Wavesand .eomprisingmtleast one high frequency amplifying stage, a demodulating st'age, and" at, least. one. audio. frequency amplifying; stage, accordinato,theinvention, the I amplifying stage, (or. oneofthem) prior, torthe rote)multi-positionswitch Mf having a cont demodul'atina. stage consists. of an. eleetron dis charge deyice. havingw in, series in its anode on? cuit. both. a circuit, resonant to. the highirequencymscillations. to beeamplifiedrandan anodew refijfitoll s un z te ll-liassz; conde serzfor thes 55f aaph'onograplnpiokup circuitcomprisihg 'a phono quenc'y stage I enablfe's two or more frequencies.

to be satisfactorily selectedwithout mutual interference; The highjfrequncy stage l comprises .amelecr tron discharge device 5 to: the control. electrode of" are supplied either" th .signa1 modulated carri'i w-aves to be amplified anddemodiie lateri or'tlie audio frequencyoscillations orig i hating; for example; in a phonograph gickup} f, The control 'electrode-i sj-connectedjto an input terminal 6 througlianu put circuit T which may include a previoiis' frequencystage, A', p1u raiity of inductancesili l'fi, illustrated as variable, may-be connected in shunt WithIa fixed capaci tance included -in are apparatusl to form resonantcircuits tune'dfto the frequenciesoffdiiierent carrierWaves supplied to; the terminal 6 desired 'on'e ofthese carrier'wai'les may be selected and su'pplierftc the control-"electrode 5'hy' neans arm movable for*"conriectin with a desired one of'th'e iridfictances-8 l$. In the lowermost; position oflthsuiitcli- I16} the contact arm' thereof engages a oontacfi button ffi to which is connected resonant circuit may comprise a fixed inductance 2| which consists of the primary winding of a high frequency transformer and a selected one of a plurality of capacitors 22-j2'|. One terminalof the capacitors 22-21 is connected to the lower terminal of the inductance 2| and'the opposite terminals of these capacitors are selectively connected through a switch arm 28 to the upper terminal of inductance 2|.

The resonant circuit connected to the anode of the device 4 is coupled in any suitable manner to the demodulating stage 2 of the receiver. This stage may comprise a crystal rectifier 29 or, alternatively, a diode or a multi-electrode electron discharge device functioning as a detector. The anode circuit of the high frequency amplifier 4 also includes an anode load resistor 30 connected in series between the lower terminal of the resonant circuit and a source of anode potential designated by the legend B+. This same potential is shown as applied to the screen electrode of device 4. The anode resistor 30 is shunted in the usual manner by a capacitor 3| of a size capable of by-passing high frequency oscillations which are not intercepted by the resonant anode circuit. 7

To ada t the circuit arrangement described for amplifying audio frequency oscillations.

discharge device 4 as a first stage of an audio frequency amp ifier, I connect the anode end of the anode resistor 30 through a. capacitor 32 directly to a point on a resistor included in the output s de of the demodulating stage 2. By. this means, when audio frequency oscillations are impressed on the input of the device 4, they set up potential variations at the anode which are conveyed through the capacitor 32 directly to the in t side of the audio frequency amplifier 3. When the arrangement is serving as a radio receiver for signal modulated carrier waves. the path including the ca acitor 32 does not affect the operation of the circuit arran ement, since t is connected on the far side of the resonant circuit connected to the anode of the high frequency am lifier 4 and tuned to the frequencv of the desired carrier wave. With this connec ion, the path pointed out provides no loss of high frequency signal strength.

When the crystal detector 29 is used as a demodulator in demodulating stage 2 of the receiver, this detector may be connected to a secondary winding 33 of the high frequency transformer, the primary winding 2! of which constitutes the inductance of the resonant circuit in the anode circuit of the high frequency amplifier 4. The other end of the secondary winding 33 is connected through a multiposi ion switch 34 to ground. The switches I4, 28 and 34 preferably are ganged for unicontrol operation and the end contacts of switches 28,

34 corresponding to contact l5 of switch l4 preferably are open-circulted so that, when :the

detector.

switch arm I4 is connected to the pickup It, the circuit of the demodulating stage 2 is opencircuited. Alternatively, the switch 34 may be eliminated and other methods used for completing the input circuit of the demodulating stage 2 when high frequency signals are received and for opening this circuit when audio frequency signals are received. 7

After passage through the detector 29, the demodulated signals are preferably smoothed by a series resistance comprising resistors 35, 35 connected in series and shunted by capacitors 31, 38. The demodulated signals are then passed through a series capacitor 39 and an additional resistor 40 which forms the main load of the An adjustable tap 4| on resistor 40 applies the demodulated signal to the input of the low frequency stage 3 and serves as a volume control for adjusting the output from the loudspeaker 42 or other reproducing device used with the receiver. The low frequency stage 3 may comprise an electron discharge device 43, the tap 4| being connected to the control electrode 4d of this receiver. The cathode of this device i3. is

connected to ground through a resistor s5 and the anode is connected through the primary winding of the usual output transformer 45 to a source of operating potential indicated by the legend B-|-. The secondary winding of transformer 46 is connected in series with the voice coil of the loudspeaker 42. q

The end of the connection through the low frequency coupling capacitor 32 to the anode end of resistor 30 and the high frequency-stage of the receiver is connected to the mid point of resistors 36, which, in turn, are connected in shunt with the audio frequency coupling capacitor'39 and volume control resistor 40 referred to above. The connection of this low frequency by pass circuit on the resistors 35, 36'is preset to give the desired amplitude of audio frequency oscillations in the input circuit of the low frequency stage 3.

If two or more high frequency stages are used" in a receiver either or any one of them may be arranged in the manner above described to constitute the first audio frequency amplifying device. If more than one of the high frequency stages is required to serve also as an audio fre-- quency amplifying stage, each of such stages should be provided with an anode resistor in the resonant circuit and the audio frequency oscillations should be taken through the. stages so employed in cascade by suitable audio frequency coupling capacitors.

While I have illustrated a particular embodiment of my invention, it will of course be understood that I do not wish to be limited thereto, since many modifications may-be made in the circuit elements employed and in their arrange-.

electron discharge device having an input circuit,

and an output circuit, switching for selectively supplying to said input circuit signal modulated carrier waves and an audio frequency wave, a resonant circuit and a load resistance connected in series in said output circuit, said resonant circuit being tuned to the frequency of the carrier waves supplied to said input circuit, dc-

'modulating means coupled to said resonant circuit, an audio frequency amplifier having an input circuit connected to said demodulating means, and fixed coupling means for supplying said waves from the junction of said load re sistance and said resonant circuit to the input circuit of said audio frequency amplifier, said coupling means comprising a series coupling capacitor capable of passing both high frequency and low frequency currents, and means for byselectively supplying to said input circuit signal modulated carrier waves and an audio frequency wave, a resonant circuit and a load resistance connected in series in said output circuit, said resonant circuit being tuned to the frequency of the carrierwaves supplied to said input circuit, demodulating means coupled to said resonant circuit, an audio frequency amplifier having an input circuit connected to said demodulating means, and fixed coupling means for supplying said waves from the junction of said load resistance and said resonant circuit to the input circuit of said audio frequency amplifier, said coupling means comprising a series coupling capacitor capable of passing both high frequency and low frequency currents, means for by-passing high frequency currents from the input circuit of said audio frequency amplifier, and means for decoupling said demodulating means from said resonant circuit when said switching means is connected to supply audio frequency signals to the input circuit of said high frequency amplifier.

3. In combination, a source of signal modulated high frequency waves, a phonograph pickup, a radio receiver comprising a high frequency amplifying stage, means for selectively connecting said high frequency amplifying stage to said source or to said pickup, said high frequency stage having an output circuit comprising a resonant circuit tunable to the frequency of said high frequency wave and a load resistance connected in series, demodulating means coupled to said resonant circuit, an audio frequency amplifier having an input circuit, said demodulating means having an output circuit coupled to the input circuit of said audio frequency amplifier, a lay-pass capacitance connected from the junction of said resonant circuit and said load resistance to the output circuit of said demodulating means, said by-pass capacitance having a value such that both high frequency currents and audio frequency currents are by-passed thereby, and means coupled with said selective connecting means for decoupling said demodulating means from said resonant circuit when said selecting means are adjusted to supply signals from said pickup to the input circuit of said high frequency amplifying stage.

JAMES MOIR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,917,898 Place July 11, 1933 2,097,874 Farnham Nov. 2, 1937 2,111,711 Van Slooten Mar. 22', 1938 OTHER REFERENCES Radio Craft, November 1940, page 268, vol. 12. 

